Aspirated smoke detectors use a network of pipes to sample air from a large area and use a highly sensitive central detector. One of the problems with aspirated smoke detectors is the time that it takes for smoke to travel from the sampling port to the central detector (transport time). A fan or blower is required to move the air toward the detector.
On one hand, it would be desirable to operate the blower at a high speed to reduce the transport time. However, operating the blower at a reduced speed will increase its life span and decrease power consumption. Decreased power consumption means that the system will require less battery capacity for situations when main power fails.
There is a need to take advantage of performance provided by higher fan, or blower speeds while at the same time taking advantage of longer operating life and reduced power consumption provided by operating at lower speeds.